GB2267538A

GB2267538A - Rotary blade pump

Info

Publication number: GB2267538A
Application number: GB9310966A
Authority: GB
Inventors: Carlo Pachetti
Original assignee: Gilardini SpA
Current assignee: Marelli Europe SpA
Priority date: 1992-06-05
Filing date: 1993-05-27
Publication date: 1993-12-08
Also published as: ES2100108A2; GB9310966D0; ITTO920484A1; ES2100108B1; ES2100108R; ITTO920484A0; DE4318418A1; FR2692009A1; IT1256843B

Abstract

A rotary blade type vacuum pump comprises a supporting body 2 for a shaft 11 for rotating a rotor 13 fitted with at least three blades 15 equally spaced angularly and slidable inside radial cavities 14 formed in the rotor 13. The outer ends of the blades (15) are maintained contacting the inner surface of a work cavity 10 in the body 2 so as to form variable-volume chambers 48 between the blades 15. The inner ends of the blades 15 simultaneously contact a pair of annular elements 70 housed in respective cavities 71 at either end of the rotor 13 and movable in planes perpendicular to the axis of the rotor 13. Lubrication passages 63, 18, 17 and 16 are provided to supply oil to cavity 71 from which it can seep into work cavity 10 to improve sealing between chambers 48. <IMAGE>

Description

1 z, ROTARY BLADE TYPE VACUUM PUMP The present invention relates to a

rotary blade type vacuum Pump ' conveniently for automotive application, for producing the vacuum required in particular for operating a power brake.

Known rotary vacuum pumps of the aforementioned type comprise a body supporting a shaft controlled by the engine, and which provides for rotating an eccentric rotor inside a work cavity. The rotor is f itted with a number of blades sliding inside cavities formed in the rotor itself, and into which oil under pressure is fed to push the outer end of the blades into contact with the inner surface of the work cavity, which is thus divided by the blades into a number of variable-volume work chambers. The strong hydrostatic thrust exerted on the inner end of the blades, in opposition to the back pressure exerted by the blades rotating over the inner surface of the work cavity which is eccentric in relation to the rotor, is produced by a relatively large supply of oil under pressure from the engine lubricating circuit to the vacuum pump.

1. 1, Though satisfactory when the engine and oil are both at operating temperature, operation of the vacuum pump as described above is obviously critical under cold operating conditions, when -starting the engine, and for a given initial period, so that the oil may fail to provide for sufficient hydrostatic thrust on the blades, which in turn, by failing to contact the inner surface of the work chamber, fail to produce the required vacuum.

To overcome the above drawback, rotary vacuum pumps have been designed wherein the blades are thrust outwards of the rotor mechanically by means of elastic elements, usually springs. Such a design, however, is relatively complex in terms of manufacture and assembly of the pump components, and hence more susceptible to breakage. In addition, the pump fails to operate satisfactorily at any engine speed, and wear on the inner surface of the work cavity is also aggravated by the relatively strong elastic thrust exerted at all times on the blades.

It is an object of the present invention to provide a rotary blade type vacuum pump designed to overcome the aforementioned drawbacks, i.e. which provides for efficient, reliable operation, and is both straightforward and cheap to produce.

According to the present invention, there is provided a rotary blade type vacuum pump comprising a supporting body for a shaft rotating a rotor fitted with at least three blades sliding inside cavities formed. in said rotor, and the outer ends of which blades are maintained contacting the inner surface of a work cavity formed in said body so as to form, between said blades, variable-volume chambers, and having respective intake and exhaust openings; characterized by the fact that the inner ends of said blades simultaneously contact at least one element movable in relation to said rotor.

A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawing.s, in which:

Fig. 1 shows a section along line I-I in Fig. 2 of the rotary blade type vacuum pump according to the present invention; Fig.s 2 and 3 show complementary parts of the Fig.1 pump along section lines II-II and III-III respectively; Fig.4 shows a partially-sectioned part view in perspective of a number of main components on the Fig.1 pump.

With reference to Fig.s 1 to 4, number 1 indicates a rotary blade type vacuum Pump comprising a conveniently die-cast supporting body 2 closed at the front by a cover 3 f itted to body 2 by means of three bolts 4 and via the interposition of an annular seal 5. At the rear end opposite the end closed by cover 3, body 2 presents a f langed portion 6 designed to f it on to a known engine block (not shown). Body 2 presents a smaller-section central portion 8, and, towards cover 3, a wider-section, cup-shaped portion 9 defining an inner work cavity 10. Portion 8 of body 2 presents a through hole 62 supporting a shaft 11, which, at one end, presents a portion 61 projecting beyond flanged portion 6, and is rotated in known manner by the engine. At the other end, shaft 11 is fitted in angularly-fixed manner inside an axial through hole 12 of a rotor 13 housed eccentrically inside work cavity 10 and having three equallyspaced radial cavities 14 extending from the outer surface of rotor 13 and terminating short of hole 12. Cavities 14 house respective blades 15 sliding inside cavities 14 so that the outer ends of the blades contact the inner surface of cavity 10.

The inner ends of blades 15 rest simultaneously on the outer surface of a pair of annular elements 70 housed in respective circular cavities 71 formed at either end of rotor 13. Elements 70 are movable in the cavity 71 plane and perpendicular to the axis of rotor 13 by the combined thrust exerted by the three blades 15 as rotor 13 is rotated and as described in more detail later on.

From the mid portion to the end f itted with rotor 13, shaft 11 presents an inner axial channel 16 for the passage of lubricating oil under pressure. Towards the dead inner end of channel 16, there is f ormed a radial hole 17 connecting channel 16 to an annular chamber 18 f ormed in the central outer surf ace of shaf t 11 at portion 8 of body 2. Portion 8 presents a conduit 63 opening out externally with a threaded portion, opening out internally at annular chamber 18 (Fig.1), and presenting an exhaust portion 80 extending towards the engine compartment and beyond flange 6. The open end of channel 16 terminates inside the cavity 71 of rotor 13 facing cover 3. Cover 3 presents a through hole 65 (Fig.3) terminating inside work cavity 10 via an intake opening 24, and communicating externally at the other end via a connecting tube 23 conveniently housing, in known manner, a known nonreturn valve (not shown) enabling only air intake from an outer tube. Inside end wall 64 of work cavity 10, in a position almost diametrically opposite intake opening 24, there terminates the exhaust opening 44 of a conduit 90, which, at the other end, communicates with an upwardsloping conduit 40 formed in portion 8 of body 2. Conduit 40 opens out externally via a threaded portion for connection to a known exhaust pipe (not shown), and communicates with a conduit portion 91 terminating inside the engine compartment beyond flanged portion 6.

Vacuum pump 1 according to the present invention operates as follows. When rotated, shaft 11 in turn rotates rotor 13, so that blades 15 define, in known manner, variable-volume chambers 48 increasing gradually from exhaust opening 44 to intake opening 24, and decreasing to a minimum at exhaust opening 44. Air is thus drawn in through opening 24 from tube 23, and is 6 exhausted through opening 44, the first portion of conduit 90 and conduit 40. Moreover, a relatively small amount of oil is f ed along conduit 63 and radial hole 17, into channel 16 in shaft 11, and into circular cavity 71 facing cover 3, from which it seeps into work cavity 10 so as to f orm an oil f ilm f or better sealing chambers 48 between blades 15. Any excess oil is drained through opening 44.

As rotor 13 is rotated, the rear ends of blades 15 are maintained permanently contacting the outer annular surf ace of element 70, so that any movement of one of the blades affects the position of the others. Consequently, the front ends of blades 15 are maintained permanently contacting the inner surface of work cavity 10, and, as rotor 13 is rotated, each element 70 describes a substantially conchoidal trajectory in the plane of circular cavity 71.

The advantages of the present invention will be clear from the foregoing description. For achieving effective outward thrust of blades 15, so that the front ends of the blades on the inner surf ace of work cavity 10 provide for effectively sealing variable-volume chambers 48, oil under pressure need no longer be supplied, by virtue of radial displacement of the blades being effected purely mechanically by annular element 70 alone, which is extremely straightforward and, hence, cheap to produce and assemble. The vacuum pump according to the present invention therefore presents no complex devices for exerting external thrust on the blades, thus providing for improved long-term reliability, and maximum efficiency under any operating condition, both when starting up the engine and at any engine speed. Moreover, the blades are no longer subject to severe oscillation due to excess oil pressure, and, by virtue of eliminating the operating clearance between the front ends of the blades and the inner surface of work cavity 10, the present invention provides for less and more even wear of said surface.

The present invention also provides for reducing power absorption, by virtue of the pump only requiring more than that required for rotating shaft 11 as opposed to exerting thrust on the blades.

To those skilled in the art it will be clear that changes may be made to the embodiment described and illustrated herein without, however, departing from the scope of the present invention. For example, the number of blades 15 may differ.

Claims

1) A rotary blade type vacuum pump (1) comprising a supporting body (2) for a shaft (11) rotating a rotor (13) fitted with at least three blades (15) sliding inside cavities (14) formed in said rotor (13), and the outer ends of which blades (15) are maintained contacting the inner surface of a work cavity (10) f ormed in said body (2) so as to f orm, between said blades (15), variable-volume chambers (48), and having respective intake and exhaust openings (24, 44); characterized by the f act that the inner ends of said blades (15) simultaneously contact at least one element (70) movable in relation to said rotor (13).

2) A vacuum pump as claimed in claim 1, characterized by the fact that said element (70) lies in a plane perpendicular to the axis of said rotor (13).

3) A vacuum pump as claimed in claim 1 or 2, characterized by the fact that said element (70) is housed in a cavity (71) formed in an end surface of said rotor (13).

4) A vacuum pump as claimed in one of the foregoing Claims, characterized by the fact that it comprises a pair of said elements (70) at either end of said rotor (13).

5) A vacuum pump as claimed in one of the foregoing Claims, characterized by the fact that said element (70) presents a circular outer profile.

6) A vacuum pump as claimed in claim 5, characterized by the fact that said element (70) is annular.

7) A vacuum pump as claimed in one of the foregoing claims, characterized by the fact that said cavities (14) housing said blades (15) are formed radially in said rotor (13).

8) A vacuum pump as claimed in Claim 7, characterized by the fact that said cavities (14) housing said blades (15) are equally spaced angularly.

9) A vacuum pump as claimed in Claim 3 or one of Claims 4 to 8 dependent on claim 3, characterized by the fact that it comprises a conduit (16) for feeding oil inside said shaft (11); said conduit (16) terminating inside said cavity (71) housing said element (70) movable in relation to said rotor (13).

10) A rotary blade type vacuum pump, substantially as described and illustrated herein with reference to the accompanying drawings.